Haemophilus ducreyi is the etiologic agent of the genital ulcer disease chancroid. H. ducreyi is a fastidious organism that is unable to synthesize heme. In vitro, H. ducreyi must be supplied with heme or heme containing compounds such as hemoglobin (Hgb) to grow. All bacteria require iron for growth, and H. ducreyi may also acquire iron from protein (HgbA). We isolated a gee, designated hgbA that encodes the 100K HgbA purpose of this study is to test the hypothesis that a hemoglobin receptor deficient mutant of H. ducreyi is impaired in its abilikty to infect human skin when compared to its isogenic parent. To test this hypothesis, we will compare the ability of H. ducreyi 35000 and its isogenic hemoglobin receptor mutant to cause experimental infection in human subjects in dose response studies. These studies will directly test whether hemoglobin receptors play a role in the ability of H. ducreyi to cause infection.